Topics in Cognition and Language: Theory, Data and Models *Perceptual scene analysis: extraction of meaning events, causality, intentionality, Theory of.
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Topics in Cognition and Language: Theory, Data and Models *Perceptual scene analysis: extraction of meaning events, causality, intentionality, Theory of Mind *Representation of meaning Operations on meaning representations reasoning, induction, analogy Sensorimotor Interaction joint attentlon, imitation *Mapping Language to meaning
Introduction Central issues of language acquisition Outline two approaches to explaining language acquisition Highlight the property of “recursivity” Discussion: identify studies that can help choose between competing hypotheses Briefly discuss future events Prepare the next meeting
Language Acquisition Learning the associations Two problems Extracting meaning from the world (by vision, audition, touch etc.) Learning the sentence-meaning relations Conceptual Representation (Meaning) Sentence Scene
(Some) Data to account for: Most of children's early language is grammatical from the adult point of view - simplified - follows adult grammatical conventions fairly well Children can generalize to use verbs in ways they have not heard before - produce some creative yet canonical utterances that they could not have heard from adults
The "Poverty of the stimulus" Obstacle The possible mappings of sentence to meaning are uncountable Language acquisition is an indeterminate problem The training data is underspecified
How to approach this question? What is the “initial state” or architecture of the learning system? How does it learn? Data to account for Specify requirements for an artificial system that can learn language*
Two Explanations Nativist: Chomsky, Pinker: Children do not learn abstract syntactic structures at all, but rather they already possess them as a part of their innate language faculty (UG). Usage Based Learning: Tomasello, Goldberg: Early utterances organized around particular concrete words and (idiom-like) phrases, not system-wide syntactic schemas. Abstract and adult-like syntactic categories and schemas emerge only gradually and in piecemeal fashion during the preschool years.
How they account for the Data: Most of children's early language is grammatical from the adult point of view Nativist: because the structure is already there Usage-based: Because they are performing “idiomlike” copy and paste. Children can generalize to use verbs in ways they have not heard before Nativist: because they exploit the innate adult syntax Usage-Based: This generalization does occurs later in development, suggesting learning.
Types of Generalization: Lexical categories (e.g. Nominal substitution): Take ___. Eat ___. Draw ___ on ___. Re-use of Grammatical constructions: new verb learned in intransitive form generalized to transitive form Creative constructions recursivity Predictions about transfer of grammatical forms: Nativist - once a gramatical form (e.g. transitive) is present it should be fully available Usage-based - transitive is element-soecific, theu becomes generalized
Transfer is progressive Productive transitive utterances in different studies. Percentage of children (or responses in some cases – see Table 1) that produced transitive utterances of a novel verb that was heard in some other sentence frame. The data points correspond to the studies listed in Table 1 (Tomasello 2000)
Children less than 3 years old - use some of their verbs in the transitive construction - namely, the ones they have heard used in that construction - but they do not use other of their verbs in the transitive construction - namely, the ones they have not heard in that construction Generalization with transitlve form
Usage-Based Learning 1. Item based imitation 2. Generalization Across types (e.g.concrete nouns) Across structures (e.g. Transitive) 3. Creative Re-combination * * What principles govern the ways in which children combine established linguistic constructions with one another creatively? Recursivity
Source of Recursivity in Language Chomsky: Syntax is source of recursive structure in semantics Jackendoff: Syntax and semantics are parrailel recursive systems Meaning has complex combinatorial structure that is not derived from syntax Extreme alternative: Semantics is the source of recursive structure
Major Issues How does the system Extract meaning from the world (by vision, audition, touch etc.) Learn the sentence-meaning relations 1. Item based imitation 2. Generalization Across types (e.g.concrete nouns) Across structures (e.g. Transitive) 3. Creative Re-combination *
Upcoming Meetings 1. June: "Vision and Language: A Robotlcs Perspective" 2. September: Mehler + Tomasello: Debate 3. Next Meeting: Data to accounz for? Recursion in language and meaning - Hauser et al. 2002 Science - Goldberg 2003 TICS
References Ray Jackendoff. Parallel constraint-based generative theories of language, Trends in Cognitive Sciences, Volume 3, Issue 10, 1 October 1999, Pages 393-400 Michael Tomasello. The item-based nature of children's early syntactic development, Trends in Cognitive Sciences, Volume 4, Issue 4, 1 April 2000, Pages 156-163